Hybrid hard drives featuring mechanical platters supplemented by a chunk of speedy solid state storage for fast access to the most frequently accessed programs seem to be where the market is headed, and Western Digital has no intention of being left behind. In fact, WD claims it's now sampling the thinnest 2.5-inch hybrid hard drive the world has ever seen.

WD's drive measures a scant 5mm thin and is slim enough to squeeze into today's slimmest notebooks, like Ultrabooks (Intel) and ultrathins (AMD). According to WD, the new drives have a footprint that's nearly 50 percent smaller than traditional 2.5-inch drives.

"Mobile devices are becoming smaller, thinner, lighter and more responsive," said Matt Rutledge, vice president of client storage solutions at WD. "Working with our technology partners, WD has developed new 5mm hard drives that enable high capacity storage along with excellent performance and superior economics to allow our customers to expand their thin offerings."

The storage maker didn't offer up too many details, saying only that its new hybrid hard drives will scale up to 500GB in capacity. Other specs are unknown at this time, and heck, WD doesn't even have a picture to share just yet. It's also unclear whether or not these will be sold as standalone drives. Currently, WD said it's partnered up with Acer and Asus to deliver its new drives in upcoming notebook models.